Interrupters for internal combustion engines include relatively movable contacts supported by a base plate and operated by a shaft driven by the internal combustion engine. These contacts interrupt at proper points of time the primary circuit of an ignition coil which stores in magnetic form the energy required for firing the spark plugs. When the primary circuit of the ignition coil is interrupted, a high voltage is generated in the secondary circuit of the ignition coil which voltage is used for firing the spark plugs, thus igniting the combustible mixture of air and gas in the cylinder or cylinders of the internal combustion engine.
The primary winding of an ignition coil is energized by a battery having a relatively low voltage, and the high voltage generated in the secondary winding of the ignition coil is distributed by a distributor to the spark plugs of the various cylinders of an internal combustion engine. The interrupter includes a cam mounted on, and driven by, the shaft of the distributor which, in turn, is driven by the internal combustion engine. The cam operates an interrupting lever which supports one of the two cooperating contacts of the interrupter, or the movable contact thereof, and causes separation of said one of the two cooperating contacts from the other or fixed contact of the interrupter.
The number of contact-operating cams which are mounted on the shaft of the distributor is equal to the number of cylinders of the internal combustion engine. Hence the shaft of the distributor of a four cylinder internal combustion engine will support four contact operating cams and will cause four interruptions of the primary circuit of the ignition coil at each revolution of said shaft. Hence each spark plug of each cylinder is supplied during each revolution of the shaft of the distributor by the intermediary of the distributor with one spark-plug-firing pulse. The relatively movable contacts of the interrupter are provided with arc-resistant overlays as, for instance, tungsten. Nevertheless the contacts of the interrupter are subject to erosion which becomes particularly apparent after the internal combustion engine of a motor vehicle has an aggregate mileage of about 10,000 miles. The aforementioned contact erosion calls for very undesirable costly service operations.
In electronic ignition systems, e.g. ignition systems including transistors, the contacts of the interrupter must carry much smaller currents than in the aforementioned interrupters of more conventional or obsolescent design. These more advanced transistorized ignition systems have been combined with reed-type contacts and are much more satisfactory than the aforementioned prior art ignition systems but are and not entirely satisfactory.
Efforts to provide interrupters requiring less servicing had but limited succes which is, in part, due to technical limitations and in part to the high cost of advanced interrupter systems. For instance, opto-electronic interrupters are subject to the formation of deposits of oil condensates on their light-sensitive elements, as a result of which opto-electronic systems may become inoperative. Other electronic ignition systems are temperature sensitive and rather impractical on account of this limitation. Most prior art electronic ignition or interrupter systems for internal combustion engines require excessive wiring.
The main object of the present invention is to provide an ignition system for internal combustion engines, and more particularly an interrupter therefor which is of the reed-switch type and which minimizes the cost of manufacture, servicing and repairs.